I have the 1600/1620 here. It does reall well with plus but wont at this point OC any 4x media, it will OC many 8x though. It reads back most dvd disk pretty well, some of my really well done minus disks evem get up to 16x.
It really doesn't do to well with minus yet but I did get a Fuji ty 02 I think to go 12x with fair results. It will only do DL media at 2.4 max.
They are still working on newer firmwares so some of the bad points may change.
My NEC 3500 does a better job with minus of course and does OC some 4x media to 8 and maybe faster, even with some of the stock firmwares. It doesn't read back DVD's as well but it is quite a bit better then my old 2500 is. It will OC DL media to 4x.
I think the BenQ has potential if they get the minus writing well and maybe get the better 4x media to go faster. It has produced excellent burns with plus media it likes, some OC to 12x even. The active servo tilt helps the quality a bit I think, same idea the Pioneer 108 uses. It supports disk testing and even does jitter but at this point it's so SLOW that it's almost useless unless you've got a hour to kill
That may also get fixed later, we'll see.
If it's going to be your only burner use plus media and it will do well, it even supports bitsetting out of the box. If you need a everything burner and don't want to wait and see if it gets better firmware get a NEC or Pioneer.